Insulating element

ABSTRACT

The invention relates to an insulation element ( 4, 4 ′), at least one nonwoven layer ( 5 ) and/or a foam layer ( 11 ) being enclosed by a film layer ( 1 ), and, to achieve a solution which is adequately permeable to water vapour but nevertheless flame-retardant, proposes that the film layer ( 1 ) consists of a flame-retardant material which is preferably closed to vapour diffusion, that the film layer ( 1 ) also has through-openings ( 2 ) and that the through-openings ( 2 ) are open to vapour diffusion.

[0001] The invention relates to an insulation element, as can be usedfor instance for heat and/or sound insulation, at least one nonwovenlayer and/or a foam layer being enclosed by a film layer.

[0002] Insulation elements of this type are already known in variousforms. Reference is made for example to DE 198 48 679 A1. Sinceinsulation elements of this type are also used with preference inaircraft construction, a flame-retardant property is consideredimportant. As disclosed by the above document, it has already beenproposed to produce the film layer from aluminium-metallizedpolyethylene or, possibly, also from inherently flame-resistantpolymers. In addition, if a foam layer is being used, it has beenproposed to use a polyimide foam layer.

[0003] On the other hand, in the case of insulation elements of thistype there is also the requirement that the enclosure should bepermeable to water vapour.

[0004] However, so far it has not been possible to combine the propertyof water vapour permeability, possibly even directionally-dependentwater vapour permeability, with the desired flame-retardant property ofthe insulating element, including with regard to its enclosure.

[0005] On this basis, the invention is concerned with the technicalobject of providing an insulation element which, on the one hand, ispermeable to vapour diffusion, in the desired way, but on the other handalso meets as far as possible the high requirements for flame-retardantproperties of the insulation element.

[0006] This object is achieved initially and substantially in the caseof the subject matter of claim 1, it being provided that the film layerconsists of a flame-retardant material, that the film layer also hasthrough-openings and that the through-openings are open to vapourdiffusion. The invention consequently takes the approach of forming thefilm layer or, as also emerges from the text below, preferably an outerfilm layer, only with a predominantly flame-retardant effect, but toleave through-openings which, although closed by the film, are open tovapour diffusion. The film layer itself can consequently be notpermeable to vapour diffusion, or possibly only much less permeable tovapour diffusion. A first, more specific embodiment of this teachingproposes that the through-openings comprise cut-outs formed in the filmlayer and that these cut-outs are respectively closed by a second filmof material which is open to vapour diffusion, disposed in a window-likemanner. Consequently, punched openings, hole-like punched openings, canbe made in the film layer and then be covered with individual,patch-like portions of a second film. For example, the second film maybe adhesively bonded to the outer film layer to the extent that thecut-outs are closed by it. A very wide range of geometries can be usedfor the cut-outs, and this also applies to the embodiments still to bedescribed below. For example, circular, rectangular, star-shaped,grid-like, and so on. In a further specific embodiment, the inventionalso proposes that the second film is disposed under the outer filmlayer and in such a way that it covers the latter even in the regionswithout through-openings. Consequently, film layers simply lying one ontop of the other may be provided, the outer film layer being formed bythe flame-retardant material and the inner film layer being formed bythe material open to vapour diffusion, with the outer film layer havingthrough-openings and the film layer which is open to vapour diffusionhaving no openings.

[0007] Furthermore, it is possible in principle for these film layers tosurround the nonwoven and/or foam layer (or possibly a number of theselayers) separately in each case and independently of one another. Inaddition, these film layers may all be welded at the edges (resulting inthe example last described in four layers on top of one other at aseam). In addition, however, it may also be provided that the outer filmlayer is laminated to the second film. Adhesive bonding can be broughtabout just by using the adhesiveness of the film layer and/or of thesecond film. The films may also be bonded to one another by a separateadhesive or a separate layer of adhesive. In the latter case, it isrecommendable, however, to provide the layer of adhesive also only in agrid-like manner, in order to preserve the vapour-diffusing property ofthe second film over as large a surface area as possible, in any eventin the regions of the through-openings.

[0008] In a further embodiment, it is also proposed that a third filmlayer is disposed under the second film layer and that the third filmlayer also consists of a flame-retardant material, but hasthrough-openings which are open to vapour diffusion.

[0009] With regard to the flame-retardant material, polyimide isparticularly suitable and is already available on the market aspolyimide films. However, a polyphenylene sulphide (PPS) film may alsobe used, for example. Also, a polyester (PET) film, a polyvinyl-fluoride(PVD) or polyvinyl-difluoride (PVDF) film.

[0010] The invention is further explained below with reference to theattached drawing, which however only shows exemplary embodiments and inwhich:

[0011]FIG. 1 shows a first schematic view of an outer film layer withthrough-openings which are open to vapour diffusion;

[0012]FIG. 2 shows a cross-section through the subject matter accordingto FIG. 1, taken in section along the line II-II;

[0013]FIG. 3 shows a schematic view of a multi-layer structure ofdifferent films for enclosing an insulation element;

[0014]FIG. 4 shows a schematic perspective view of a first exemplaryembodiment of an insulation element;

[0015]FIG. 5 shows a cross-sectional view of a second exemplaryembodiment of an insulation element.

[0016] Shown and described, initially with reference to FIG. 1, is afilm layer 1 for an insulation element, as represented for example inFIG. 4 or 5.

[0017] It is pertinent that the film layer 1 consists of afire-retardant material, in this case polyimide. It is also ofsignificance that this film layer 1 has through-openings 2, which areopen to vapour diffusion.

[0018] The through-openings 2 are made open to vapour diffusionspecifically by a second film layer 3, covering the openings 2 andlaminated onto the film layer 1, the second film layer 3 consisting ofmaterial which is open to vapour diffusion.

[0019] It can be gathered from the cross-sectional representationaccording to FIG. 2 that a through-opening 2 is formed in the film layer1 by a punching process, which leaves behind a corresponding hole. Thishole is closed, while allowing vapour diffusion, by being covered on oneside by means of the film layer 3 which is open to vapour diffusion.

[0020] In principle, the film layer 3 may also be applied to both sidesof the through-opening 2. In practice, however, it is recommendable toprovide the film layer 3 on the inner side of the film layer 1, that isthe side towards the nonwoven and/or foam layer.

[0021] Represented in FIG. 3 is a further exemplary embodiment, in whichthe enclosure of the insulation element comprises three layers, a filmlayer 1, a second film layer 3′ and a third film layer 11.

[0022] The film layer 1 is identical to the film layer 1 according toFIG. 1, but here the through-openings 2 are left free, that is to say itis not envisaged for this opening to be covered with a film which isopen to vapour diffusion. Rather, they are actual openings which are notclosed by anything.

[0023] However, here a second film layer 3′, which corresponds in termsof material to the second film layer 3 according to the exemplaryembodiment of FIGS. 1 and 2, is disposed under the film layer 1 andcompletely covers it. Consequently, this is a film layer which is opento vapour diffusion. It is integral throughout, that is to say has nothrough-openings.

[0024] Furthermore, a third film layer 1′ is disposed under the secondfilm layer 3′. In terms of material, this is again a flame-retardantfilm, that is to say it is correspondingly, or in terms of material,identical to the film layer 1. It is also formed in the same way withregard to the through-openings as the film layer 1. However, in practicethe through-openings 2′ of the third film layer 1′ may be disposed insuch a way that they are not located congruently in relation to thethrough-openings 2 of the film layer 1. The through-openings 2 of thefilm layer 1 and of the third film layer 1′ are offset in relation toone another.

[0025] Represented in FIG. 4 is a first actual exemplary embodiment, afilm layer 1 with through-openings 2 which are open to vapour diffusionbeing used here in a way corresponding to the exemplary embodiment ofFIGS. 1 and 2.

[0026] The insulation element 4 represented correspondingly comprises afilm layer 1, which encloses at the front and rear a nonwoven layer 5located in between.

[0027] The through-openings 2 which are open to vapour diffusion aremerely indicated. An important point, however, which also can be appliedwith regard to the further exemplary embodiments and in general, is thatthe through-openings 2 which are open to vapour diffusion are onlyprovided here in a central region of the insulation element, whereas aperipheral edge region is not provided with these openings 2.Alternatively, however, it is also possible to provide thevapour-diffusion openings 2 in a regular distribution over the entireouter surface of the insulation element 4.

[0028] Instead of the nonwoven layer 5, a polyimide foam sheet may alsobe provided.

[0029] With regard to the nonwoven layer, it may be made of materialcomprising a polymer, such as for example PPS or a mixture of PPS andcopolyester or other organic or inorganic fibres. In particular, it mayalso be made of melamine-resin fibres, exclusively or in a mixture. Theweight per unit area of the nonwoven layer may lie between 50 and 800g/m².

[0030] The nonwoven layer, its fibres, is also preferably inherentlyflame-resistant.

[0031] The film layer 1 has a small thickness, for instance between 10and 50μ, preferably around 20μ. In the region of the through-openings 2,the film layer provided there, which is open to vapour diffusion, may beof the same thickness.

[0032] It is also important that fibres, which are indicated by thegridwork of lines in the drawing, are laminated onto the films 1, 2, butalso the second film layers 3 or 3′. They may be glass fibres, or elsemelamine-resin fibres and/or polyester fibres. The fibres are onlyprovided on one side of the film layers 1 and 2 or 3, 3′. The gridworklines are spaced between approximately 1 and 5 mm apart. Crisscrossingfibres are respectively provided.

[0033] As a further detail, the middle nonwoven layer 5 is covered bynonwoven layers 6, 7, which in each case cover them entirely but arethinner.

[0034] In the case of the exemplary embodiment of FIG. 5, an insulationelement 4′ is represented, here only in cross-section, the enclosure ofwhich is formed in a way corresponding to the exemplary embodiment ofFIG. 3.

[0035] With regard to the enclosure, it is firstly evident that itcomprises three layers on each side, so that in the edge region 8 thereis a six-layer formation.

[0036] The outermost layer is in each case a film layer 1 of a polyimideor PPS material with through-openings 2, as described with regard toFIG. 3. Under that is the film layer 3 of material open to vapourdiffusion. Under that in turn, as a third layer, is the film layer 1′with through-openings 2′.

[0037] In the edge region 8, all six layers are welded to one another.

[0038] As a further detail, the insulation element 4′represented has twononwoven layers 9 and 10, which may be formed from similar or dissimilarmaterial. The fibres of the nonwoven material consist of a polymer, suchas for example PPS or a mixture of PPS and copolyester and other organicand inorganic fibres, the weights per unit area of the nonwoven layers9, 10 lying between 50 and 800 g/m²Moreover, the upper nonwoven layer 9may comprise a melt-blown nonwoven and the lower nonwoven layer 10 maycomprise a thermobonded volume nonwoven and/or a foam layer.

[0039] The fibres of the nonwoven layers 9, 10 are thermoplastic andinherently flame-resistant. The granules from which the nonwoven fibresare obtained have a specific melt flow viscosity. The nonwovens are alsoresistant to hydrolysis. Moreover, they are acoustically absorbent anddamping. In addition, they have a heat-insulating effect. They may alsobe given an intumescent finish, to further enhance the fire behaviour.

[0040] The middle layer 11 takes the form of a foam layer, in particulara polyimide foam layer. As illustrated by the sectional representationof FIG. 5, this foam layer 11 is uneven and three-dimensionallystructured. In practice, the formation is chosen such that the foamlayer 11 proceeds in planar extent in a zigzag form. The choice of apolyimide foam means that, with a comparatively large volume, a verylightweight middle layer is obtained for forming the insulation element4′.

[0041] As a further detail, the foam layer 11 comprises a cut-to-sizepolyimide foam, the thickness and/or the angled progression with respectto the vertical of the zigzag links 12 allowing a desired soundabsorption behaviour to be set. In the exemplary embodiment shown, amaterial thickness d of approximately 8 mm has been chosen, with anoverall height h of the foam layer 11 of approximately 24 mm. Thethicknesses of the nonwoven layers 9, 10—in the uncompressed state—areapproximately one third to one tenth of the middle foam layer 11. Theabsolute thicknesses of the nonwoven layers 9, 10 lie in the range from0.5 to 5 mm.

[0042] With regard to the film layers 1, 3, 2′, they may befibre-reinforced films in the case of one, two or all three of the filmlayers. The thicknesses are very small in each case. The absolutethickness of a film layer 1, 3, 1′ lies between 10 and 50μ, preferablyaround 20μ. The density of such a film is around 0.9 to 1.4 g/m³. Thefilm layer 3 which is open to vapour diffusion is thermoplastic and alsopreferably resistant to hydrolysis and flame-proof. The film layers 1′of the front side and rear side may, as a further preference, also havedifferent water vapour permeabilities, also with regard to differentdirectional characteristics (only letting water vapour in or out).

[0043] With regard to the film layers 1 and 1′, they may be inherentlyflame-resistant polymers. Fibres 13, which in the case of the exemplaryembodiment are provided only on one side of the lower film layer 1′, maybe glass fibres, or else melamine-resin fibres, which are laminated-on.

[0044] Outside the edge regions, the film layers 3, 1′ and 1 are onlyplaced one on top of the other. With regard to the insulation element asa whole, this produces as it were a cushion with an enclosure formed bythe three-layered outer films.

[0045] All features disclosed are (in themselves) pertinent to theinvention. The disclosure content of the associated/attached prioritydocuments (copy of the prior application) is hereby fully incorporatedin the disclosure of the patent application, including for the purposeof incorporating features of these documents in claims of the presentpatent application.

1. Insulation element (4, 4′), at least one nonwoven layer (5) and/or afoam layer (11) being enclosed by a film layer (1), characterized inthat the film layer (1) consists of a flame-retardant material which ispreferably closed to vapour diffusion, in that the film layer (1) alsohas through-openings (2) and in that the through-openings (2) are opento vapour diffusion.
 2. Insulation element according to claim 1 or inparticular according thereto, characterized in that the through-openings(2) comprise cut-outs (2) formed in the film layer (1) and in that thecut-outs (2) are closed by a second film (3) of material which is opento vapour diffusion, disposed in a window-like manner.
 3. Insulationelement according to one or more of the preceding claims or inparticular according thereto, characterized in that the through-openings(2) are formed as circular holes.
 4. Insulation element according to oneor more of the preceding claims or in particular according thereto,characterized in that the second film (3) is disposed as a second filmlayer under the outer film layer (1) and in such a way that it coversthe latter even in the regions without through-openings (2). 5.Insulation element according to one or more of the preceding claims orin particular according thereto, characterized in that the second film(3) and the outer film layer (1) are laminated to each other. 6.Insulation element according to one or more of the preceding claims orin particular according thereto, characterized in that a third filmlayer (1′) is disposed under the second film layer (3) and in that thethird film layer (1′) also has through-openings (2′) which are open tovapour diffusion.
 7. Insulation element according to one or more of thepreceding claims or in particular according thereto, characterized inthat the third film layer (1′) consists of a flame-retardant material.8. Insulation element according to one or more of the preceding claimsor in particular according thereto, characterized in that theflame-retardant material is polyimide, PPS, PET, PVF or PVDF.